1. Field of the Invention
The present invention relates generally to medicine, and more specifically to ophthalmology, and has particular reference to a corrective intraocular lens which finds successful application for treatment of myopia, hyperopia, astigmatism, and other eye diseases.
2. Description of the Prior Art
Correction of such eyesight deficiencies as myopia, hyperopia, and the like has conventionally involved the use of glasses or contact lenses. However, correction with the use of such devices is temporary, since such devices must be placed and removed periodically, for example, while skiing, swimming and the like.
Permanent correction of eyesight is performed with the aid of keratotomy. One of these techniques includes removal of the corneal layer and its reshaping, while another technique includes the making of a multiplicity of radial cuts into the corneal layer to adjust the curvature thereof, followed by healing. The aforesaid kerato-refractive surgical techniques are of an irreversible nature and suffer from inadequate accuracy of prognostication of the postoperative refractive effect.
Intraocular lenses or lenticuli have been used to solve these problems, but they are intended largely for correction of postcouching aphakia.
There has been provided a corrective lens for use in conjunction with the intact natural lens, such as that described in U.S. Pat. No. 4,585,456 issued on Apr. 29, 1986 to Blackmore. This corrective lens employs an optical body formed of a material biocompatible with the eye and having a concave posterior surface with a curvature that fits the curvature of the external surface of the natural lens. The aforesaid optical body includes a means for positioning it so that it is adjacent to the natural lens. To retain the corrective lens in this position, provision is made for supporting elements shaped as, for example, open loops associated with the positioning means as is known in the art with respect to intraocular lenses. When inserting such a corrective lens within the patient's eye, the supporting elements are placed in the ciliary sulcus. However, such an attachment is subject to various disadvantages inherent in fastening of an intraocular lens in the ciliary sulcus and, in particular, the rather frequent danger-of inflammation of the ocular tissues. Moreover, as it has been confirmed by practical experience, such an attachment might be inadequately reliable and results in dislocation or displacement of the corrective lens.
There is known in the prior art an intraocular lens which includes an optical body having a posterior concave surface, an anterior surface and a periphery. The lens further includes a positioning element in surrounding relation to the optical body and connected to the periphery thereof, the positioning element including a periphery and a posterior concave surface that forms a smooth continuation of the optical body posterior concave surface and which has a curvature identical to the curvature of the optical body posterior concave surface. Finally, the lens includes a supporting element including a proximal portion connected with the positioning element periphery, a distal portion adapted to contact a zonal ligament, a posterior concave surface on one side of the supporting element between the proximal portion thereof and the distal portion, the supporting element posterior concave surface forming a smooth continuation of the positioning element posterior concave surface and having a curvature identical to the curvature of the positioning element posterior concave surface. The supporting element further includes an anterior surface on an opposite side of the supporting element between the proximal portion and the distal portion thereof, the supporting element anterior surface having a concavity which has an opposite direction of curvature from the supporting element posterior concave surface, such that the supporting element non-linearly decreases in thickness between the supporting element anterior surface and the supporting element posterior concave surface, from the proximal portion to the distal portion thereof.
However, with such corrective lens for use in conjunction with the intact natural lens, the lens is secured to the zonal ligaments. As a result, the lens is at a fixed position in the eye. However, in some instances, the pupil of the eye may be off-center, for example, offset upwardly and toward the nose. Although this lens functions well when the pupil of the person is centered in the eye, this lens does not function as well when the pupil is off-center. This is because the lens is fixed to the zonal ligaments at a predetermined position in the eye. In such case, the corrective lens is fixed and can only contract and expand.
Further, because the lens is fixed in the eye, it is limited to a relatively small range of diopters, and has, for example, an upper limit of use with a -12 diopter.
Still further, with the aforementioned corrective lens, because there is a thickened portion at the intersection of the positioning element with the optical body, when the lens is inserted in the eye, a force is applied to the iris. As a result, the iris is biased into a substantially frusto-conical configuration. This is disadvantageous, and rather, it is desirable that the iris remain in its original substantially planar configuration.
Also, with corrective lenses that are fixed in the eye, it is necessary to remove portions of the iris in order to provide circulation of liquid in the eye, which is essential to normal operation of the eye.